Inverter unit

ABSTRACT

An inverter unit includes a first circuit board and a second circuit board arranged at a predetermined space so as to face each other. Each of the first circuit board and the second circuit board has a main circuit forming area. A plurality of power devices are mounted in the main circuit forming area of the first circuit board and form a main circuit. A plurality of capacitors are electrically connected to the plurality of the power devices and mounted in the main circuit forming area of the second circuit board. A control circuit controls the operation of the main circuit. The second circuit board includes a control circuit forming area separated from the main circuit forming area. The control circuit includes a first control circuit formed in the control circuit forming area of the second circuit board.

BACKGROUND OF THE INVENTION

The present invention relates to an inverter unit which has a pair ofcircuit boards arranged at a predetermined space to face each other.

Japanese Unexamined Patent Publication No. 2000-133768 discloses a powersemiconductor module. The power semiconductor module includes aninsulating metal substrate in which a metal plate, an insulating layerand copper foil patterns are laminated in this order. The copper foilpatterns include a main circuit pattern area having power semiconductordevices such as IGBTs (Insulated Gate Bipolar Transistor) and a controlcircuit pattern area having control semiconductor devices. The maincircuit pattern area and the control circuit pattern area are separatedfrom each other by a linear separator.

In the above-described power semiconductor module wherein the maincircuit pattern area having power semiconductor devices and the controlcircuit pattern area having control semiconductor devices are separatedfrom each other by the linear separator, the noise developed by theswitching of the power semiconductor devices can be suppressed fromtransmitting to the control semiconductor devices through the metalplate.

There has been an increasing demand for downsizing and increasing theoutput power of inverter units as a semiconductor module. To meet suchdemand, it is proposed that circuit components of the inverter unitincluding a plurality of power devices, a plurality of capacitors andcontrol devices should be arranged separately on a plurality of circuitboards and such circuit boards should be arranged at a predeterminedspace from each other. In such an inverter unit, large current flows inthe main circuit including the power devices and the capacitors whilerelatively small current flows in the control circuit including thecontrol devices controlling the switching of the main circuit ascompared to the current in the main circuit. Though the parts of aninverter unit have different sizes and shapes, mixed arrangement ofparts for the main circuit and parts for the control circuit on a singlecircuit board of the inverter unit may enhance the mounting density ofparts and realize downsizing of the inverter unit.

However, the above-described inverter units have problems that noiseoccurs during the switching of the power devices and high heatgeneration occurs due to large current flowing in the main circuit.Therefore, transmission of noise and heat to the control circuit of theinverter unit need be suppressed.

The present invention is directed to providing an inverter unit thatsuppresses the influence of the noise development of power devices andthe heat generation of the main circuit on the control circuit of theinverter unit.

SUMMARY OF THE INVENTION

In accordance with an aspect of the present invention, an inverter unitincludes a first circuit board and a second circuit board arranged at apredetermined space so as to face each other. Each of the first circuitboard and the second circuit board has a main circuit forming area. Aplurality of power devices are mounted in the main circuit forming areaof the first circuit board and form a main circuit. A plurality ofcapacitors are electrically connected to the plurality of the powerdevices and mounted in the main circuit forming area of the secondcircuit board. A control circuit controls the operation of the maincircuit. The second circuit board includes a control circuit formingarea separated from the main circuit forming area. The control circuitincludes a first control circuit formed in the control circuit formingarea of the second circuit board.

Other aspects and advantages of the invention will become apparent fromthe following description, taken in conjunction with the accompanyingdrawings, illustrating by way of example the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

FIG. 1 is an exploded perspective view of an inverter unit according toan embodiment of the present invention;

FIG. 2 is an equivalent circuit view of a main circuit of the inverterunit of FIG. 1;

FIGS. 3A and 3B are plain views of a main circuit board and a capacitorcircuit board shown in FIG. 1, respectively; and

FIGS. 4A and 4B are plain views of a main circuit board and a capacitorcircuit board, respectively, according to a variation of the embodimentof the present invention.

The following will describe the inverter unit according to theembodiment of the present invention with reference to the accompanyingdrawings. In the drawings, the same parts or the parts having the samefeatures are designated by the same symbols and the overlappingdescription thereof will be omitted. It is noted that some elements inthe drawings are shown with dimensional ratio different from that of theactual element for the clarity of the drawings.

Referring to FIG. 1, numeral 1 designates an inverter unit according tothe embodiment of the present invention. The inverter unit 1 is athree-phase inverter unit for driving a three-phase motor.

As shown in FIG. 2, the main circuit of the inverter unit 1 is suppliedwith power across a positive input P and a negative input N and includessix power devices Q1, Q2, Q3, Q4, 05, Q6 such as a MOSFET (Metal OxideSemiconductor Field Effect Transistor) connected in three-phase bridgeconfiguration and flywheel diodes D1, D2, D3, D4, D5, D6 connected ininversely parallel to the power devices Q1, Q2, Q3, Q4, 05, Q6,respectively. IGBTs may be used as the power devices Q1, Q2, Q3, Q4, 05,06.

The power devices Q1, Q2 are serially connected across the positiveinput P and the negative input N. A U-phase output U is connected to ajunction between the power devices Q1, Q2. The power devices Q3, Q4 areserially connected across the positive input P and the negative input N.A V-phase output V is connected to a junction between the power devicesQ3, Q4. The power devices Q5, Q6 are serially connected across thepositive input P and the negative input N. A W-phase output W isconnected to a junction between the power devices Q5, Q6.

A capacitor C is connected across the positive input P and the negativeinput N. The power devices Q1, Q2, Q3, Q4, Q5, Q6 are connected to adrive circuit A which controls the switching of each power device. InFIG. 2, the respective power devices Q1, Q2, Q3, Q4, Q5, Q6 equivalentlydenote device groups each including a plurality of power devices or, forexample, four power devices connected in parallel to each other.

Referring to FIGS. 1, 3A and 3B, the following will describe thestructure of the inverter unit 1. The inverter unit 1 includes a maincircuit board 10 (a first circuit board), a capacitor circuit board 20(a second circuit board), a plurality of power devices 30, a pluralityof capacitors 50, a control circuit 60 (a first control circuit), aplurality of output terminals 70, a plurality of relay electrodes 80 anda plurality of current detectors 90.

The main circuit board 10 and the capacitor circuit board 20 arearranged in close proximity at a predetermined space by a spacer memberM to face each other. The spacer member M is made of an insulatingmaterial such as resin or ceramic formed in a frame shape and arrangedalong the side edges of the main circuit board 10 and the capacitorcircuit board 20. The spacer member M keeps constant the distancebetween the main circuit board 10 and the capacitor circuit board 20.The main circuit board 10 includes an IMS (Insulating Metal Substrate)and is disposed on a heat sink H which is formed of a flat metal platesuch as aluminum or copper. The capacitor circuit board 20 includes aknown printed circuit board.

The power devices 30 are mounted on the main circuit board 10. In thepresent embodiment, a plurality of power devices or, for example, fourpower devices 30 connected in parallel form an upper arm element and alower arm element of each phase. Specifically, the power devices 30correspond to the power devices Q1, Q2, Q3, Q4, Q5, Q6 in FIG. 2. Themain circuit board 10 has a main circuit forming area in which the powerdevices 30 are mounted thereby to form part of the main circuit. Thecapacitors 50 are mounted on the capacitor circuit board 20 andelectrically connected to the power devices 30. The capacitors 50correspond to the capacitor C shown in FIG. 2. The capacitor circuitboard 20 has a main circuit forming area (described later as the areaA1) in which the capacitors 50 are mounted.

The control circuit 60 is formed on the capacitor circuit board 20 andused for various controlling purposes e.g. controlling the switching ofthe power devices 30 of the main circuit of the main circuit board 10.The control circuit 60 corresponds to a part of the drive circuit A inFIG. 2. The output terminals 70 of the respective phases, or U-phase,V-phase, W-phase are arranged on the main circuit board 10 and projectthrough holes 20H formed in the capacitor circuit board 20.

The output terminals 70 correspond to U-phase, V-phase and W-phaseoutput terminals in FIG. 2.

The relay electrodes 80 are mounted on the main circuit board 10 andelectrically connected to predetermined wiring patterns on the capacitorcircuit board 20 when the main circuit board 10 and the capacitorcircuit board 20 are assembled together in facing relation to eachother. The relay electrodes 80 correspond to the positive input P andthe negative input N in FIG. 2.

The current detectors 90 are arranged on the capacitor circuit board 20for detecting output current from the main circuit. Specifically, eachcurrent detector 90 is composed of a U-shaped core 91 made of a magneticsteel plate and formed around the output terminal 70 and a currentdetecting element 92 disposed in the opening between the opposite endsof the U-shaped core 91. A hall element is used as the current detectingelement 92.

As shown in FIG. 3B, the capacitor circuit board 20 has a substantiallyrectangular plate shape. The capacitor circuit board 20 is formed by anarea A1 (the main circuit forming area) and an area A2 (the controlcircuit forming area) which are arranged separately extending along thelong sides 21, 22 of the rectangular capacitor circuit board 20. Each ofthe areas A1 and A2 is of a substantially rectangular shape.

The area A1 and the area A2 are separated from each other by asubstantially linear boundary region B2 (a second boundary region)extending along the long sides of the rectangular capacitor circuitboard 20. For example, the boundary region B2 may be formed by astraight cut formed in the wiring pattern of the capacitor circuit board20. The holes 20H of the capacitor circuit board 20 are formed in thearea A1 of the capacitor circuit board 20.

The capacitors 50 are arranged in the area A1 of the capacitor circuitboard 20. The holes 20H are formed in the area A1 of the capacitorcircuit board 20 as described above, so that the output terminals 70projecting from the holes 20H are also arranged in the area A1 of thecapacitor circuit board 20. Terminals (not shown in the drawing) forelectrical connection to the relay electrodes 80 are also arranged inthe area A1 of the capacitor circuit board 20. The control circuit 60 isarranged in the area A2 of the capacitor circuit board 20.

Thus, in the capacitor circuit board 20, the components such as thecapacitors 50 and the output terminals 70 of the main circuit in whichrelatively large current flows are collectively arranged in the area A1,while the control circuit 60 in which relatively small current flows isarranged in the area A2 of the capacitor circuit board 20. That is, inthe capacitor circuit board 20, the main circuit and the control circuitare arranged separately from each other.

As described above, the inverter unit 1 includes the main circuit board10 and the capacitor circuit board 20 that are arranged at apredetermined space to face each other, the power devices 30 arranged onthe main circuit board 10, the capacitors 50 and the control circuit 60arranged on the capacitor circuit board 20.

Specifically, the capacitor circuit board 20 has the area A1 and thearea A2 that are separate from each other. The capacitors 50 arearranged in the area A1 and the control circuit 60 is arranged in thearea A2 of the capacitor circuit board 20, respectively.

That is, in the capacitor circuit board 20, the capacitors 50 thatcompose the main circuit with the power devices 30 and in which maincurrent flows and the control circuit 60 in which control current flowsare arranged separately without being mixed on the capacitor circuitboard 20. The capacitor circuit board 20 has two separate areas namelythe area A1 in which large current flows and the area

A2 in which small current flows. Therefore, the inverter unit 1according to the present embodiment can reduce its size and suppress theinfluence of the noise developed during switching of the power devices30 and of the heat of the main circuit on the control circuit 60 by theseparate arrangement of the power devices 30 in the main circuit board10, the capacitors 50 and the control circuit 60 in the capacitorcircuit board 20.

In the inverter unit 1, the provision of the area A1 and the area A2divided from each other by the substantially linear boundary region B2permits separate arrangement of the area in which large current flowsand the area in which small current flows. Furthermore, the provision ofthe current detecting elements 92 in the area A2 permits increaseddetection sensitivity of the current detectors 90 by suppressing theinfluence of noise.

The above-described embodiment has dealt with an embodiment of theinverter unit according to the present invention. The present inventionis not limited to the above-described embodiment, but it may bepracticed in various ways as exemplified below.

Referencing to FIGS. 4A and 4B, an inverter unit 1 according to avariation of the first embodiment of the present invention includes amain circuit board 10A corresponding to the main circuit board 10 ofFIG. 1 and a control circuit 40 which is formed on the main circuitboard 10A as a second control circuit and corresponds to a part of thecontrol circuit 60 on the capacitor circuit board 20 of FIG. 1. Thecontrol circuit 40 may be a drive circuit A controlling the switching ofthe power devices 30.

Like the capacitor circuit board 20, the main circuit board 10A has asubstantially rectangular plate shape. The main circuit board 10A isseparated into an area A3 (a main circuit forming area) and an area A4(a control circuit forming area) by a boundary region B1 (a firstboundary region) extending along the long sides 11, 12 of therectangular main circuit board 10A. The area A3 and the area A4 are of asubstantially rectangular shape.

The power devices 30, the output terminals 70 and the relay electrodes80 are arranged in the area A3 of the main circuit board 10A.Specifically, four power devices 30 for each arm element are disposed inthe area A3 of the main circuit board 10A along the short sides of therectangular main circuit board 10A. The output terminals 70 and therelay electrodes 80 are arranged in the center of the area A3 thatextends along the long sides of the main circuit board 10A and betweentwo groups of the power devices 30 for the respective arm elements,namely one group of power devices 30 adjacent to the long side 11 of themain circuit board 10A and the other group adjacent to the boundaryregion B1. The control circuit 40 is arranged in the area A4 of the maincircuit board 10A.

Thus, in the main circuit board 10A, the components such as the powerdevices 30, the output terminals 70 and the relay electrodes 80 thatcompose the main circuit and in which relatively large current flows arecollectively arranged in the area A3, while the control circuit 40 inwhich relatively small current flows is arranged in the area A4 of themain circuit board 10A. That is, in the main circuit board 10A, the maincircuit and the control circuit are also arranged separately from eachother.

With the main circuit board 10A and the capacitor circuit board 20assembled together, the area A1 of the capacitor circuit board 20 ispositioned to face the area A3 of the main circuit board 10A and thearea A2 of the capacitor circuit board 20 is positioned to face the areaA4 of the main circuit board 10A. Therefore, the areas A1, A2 of thecapacitor circuit board 20 are formed extending in the same direction asthe areas A3, A4 of the main circuit board 10A. That is, the area A3 ofthe main circuit board 10A and the area A1 of the capacitor circuitboard 20 are positioned on the same side of the inverter unit 1. Theareas A1, A2 of the capacitor circuit board 20 are separated by theboundary region B2 extending in the same direction as the boundaryregion B1 of the main circuit board 10A.

As described above, the capacitors 50 are arranged in the area A1 of thecapacitor circuit board 20. With the main circuit board 10A and thecapacitor circuit board 20 assembled together in facing relation, thepower devices 30 on the main circuit board 10A and the capacitors 50 onthe capacitor circuit board 20 are arranged in close proximity to faceeach other.

The inverter unit 1 according to the above-described variation of theembodiment of the present invention includes the main circuit board 10Aand the capacitor circuit board 20 that are arranged at a predeterminedspace to face each other, the power devices 30 and the control circuit40 arranged on the main circuit board 10A, and the capacitors 50 and thecontrol circuit 60 arranged on the capacitor circuit board 20. The maincircuit board 10A has the area A3 and the area A4 that are separatedfrom each other. The capacitor circuit board 20 has the area A1 and thearea A2 that are separated from each other.

In the main circuit board 10A, the power devices 30 and the controlcircuit 40 are arranged separately in the area A3 and the area A4,respectively. In the capacitor circuit board 20, the capacitors 50 andthe control circuit 60 are arranged separately in the area A1 and thearea A2, respectively. That is, the power devices 30 and the capacitors50 that compose the main circuit, and the control circuits 40, 60 arearranged separately without being mixed on the main circuit board 10Aand the capacitor circuit board 20, respectively. Therefore, theinverter unit 1 according to the variation of the embodiment of thepresent invention permits to suppress the influence of the noisedevelopment and the heat generated in the main circuit on the controlcircuit.

In the inverter unit 1 according to the variation of the embodiment ofthe present invention, with the main circuit board 10A and the capacitorcircuit board 20 assembled in close proximity to face each other, thepower devices 30 on the main circuit board 10A and the capacitors 50 onthe capacitor circuit board 20 are positioned in close proximity to faceeach other. With the main circuit board 10A and the capacitor circuitboard 20 assembled together, the output terminals 70 and the relayelectrodes 80 are located in the area A3 of the main circuit board 10Aand in the area A1 of the capacitor circuit board 20. In the inverterunit 1 according to the variation of the embodiment of the presentinvention wherein the main circuit is arranged collectively, the circuitinductance of the main circuit is reduced and the pattern length of themain circuit is shortened, with the result that the noise developmentand the heat generation in the main circuit are suppressed.

In the inverter unit 1 according to the variation of the embodiment ofthe present invention wherein a part of the control circuit, or thecontrol circuit 40, also arranged on the main circuit board 10A,mounting parts with high density and reduction in size of the inverterunit may be achieved. As compared to a case that the control circuit isarranged only on the capacitor circuit board 20, arrangement of parts ofthe control circuit both on the capacitor circuit board 20 and the maincircuit board 10 permits to reduce the size of the capacitor circuitboard 20 and the main circuit board 10. Furthermore, in the inverterunit 1 according to the variation of the embodiment of the presentinvention wherein the area A3 and the area A4 of the main circuit board10A are separated from each other by the boundary region B1, the area inwhich large current flows (area A3) and the area in which small currentflows (area A4) are separated.

Furthermore, in the inverter unit 1 according to the variation of theembodiment of the present invention, the areas A1, A3 in which largecurrent flows and the areas A2, A4 in which small current flows areseparated not only in the main circuit board 10A and the capacitorcircuit board 20, respectively, but also in the entire inverter circuit1. As a result, the influence of the noise development due to theswitching of the power devices 30 and the heat generation of the maincircuit on the control circuit can be suppressed effectively.

What is claimed is:
 1. An inverter unit comprising: a first circuitboard and a second circuit board arranged at a predetermined space toface each other and having respective main circuit forming areas; aplurality of power devices mounted in the main circuit forming area ofthe first circuit board; a main circuit including the plurality of powerdevices; a plurality of capacitors electrically connected to theplurality of the power devices and mounted in the main circuit formingarea of the second circuit board; and ca control circuit controlling theoperation of the main circuit, wherein the second circuit board includesa control circuit forming area separated from the main circuit formingarea and the control circuit includes a first control circuit formed inthe control circuit forming area on the second circuit board.
 2. Theinverter unit according to claim 1, wherein the first circuit boardincludes a control circuit forming area separated from the main circuitforming area, wherein the control circuit includes a second controlcircuit formed in the control circuit forming area on the first circuitboard.
 3. The inverter unit according to claim 2, wherein the maincircuit forming area and the control circuit forming area on the firstcircuit board are separated from each other by a first substantiallylinear boundary region, wherein the main circuit forming area and thecontrol circuit forming area on the second circuit board are separatedfrom each other by a second substantially linear boundary regionextending in the same direction as an extending direction of the firstboundary region.
 4. The inverter unit according to claims 1, wherein themain circuit forming area on the first circuit board and the maincircuit forming area on the second circuit board are positioned on thesame side of the inverter unit.
 5. The inverter unit according to claims1, further comprising: a current detector detecting output current fromthe main circuit, wherein a current detecting element of the currentdetector is disposed in the control circuit forming area of the secondcircuit board.